/* -*- mode: c; c-file-style: "k&r" -*-

strnatcmp.c -- Perform 'natural order' comparisons of strings in C.
Copyright (C) 2000, 2004 by Martin Pool <mbp sourcefrog net>

This software is provided 'as-is', without any express or implied
warranty.  In no event will the authors be held liable for any damages
arising from the use of this software.

Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
*/


/* partial change history:
*
* 2004-10-10 mbp: Lift out character type dependencies into macros.
*
* Eric Sosman pointed out that ctype functions take a parameter whose
* value must be that of an unsigned int, even on platforms that have
* negative chars in their default char type.
*/

/*
* 2013-08-23: Skip leading zero's for any run of digits, except
*             when a decimal point was seen immediatley before.
*             Patch by LoRd_MuldeR <mulder2@gmx.de>
*/

#include <ctype.h>
#include <string.h>
#include <assert.h>
#include <stdio.h>

#include "../include/strnatcmp.h"

typedef MUtils::Internal::NaturalSort::nat_char nat_char;

/* These are defined as macros to make it easier to adapt this code to
* different characters types or comparison functions. */
static inline int nat_isdigit(nat_char a)
{
	return iswdigit(a);
}

static inline int nat_isspace(nat_char a)
{
	return iswspace(a);
}

static inline nat_char nat_isdecpoint(nat_char a)
{
	return (a == L'.') || (a == L',');
}

static inline nat_char nat_toupper(nat_char a)
{
	return towupper(a);
}

static int compare_right(nat_char const *a, nat_char const *b)
{
	int bias = 0;

	/* The longest run of digits wins.  That aside, the greatest
	value wins, but we can't know that it will until we've scanned
	both numbers to know that they have the same magnitude, so we
	remember it in BIAS. */
	for (;; a++, b++)
	{
		if (!nat_isdigit(*a) && !nat_isdigit(*b))
			return bias;
		else if (!nat_isdigit(*a))
			return -1;
		else if (!nat_isdigit(*b))
			return +1;
		else if (*a < *b)
		{
			if (!bias)
				bias = -1;
		}
		else if (*a > *b)
		{
			if (!bias)
				bias = +1;
		}
		else if (!*a && !*b)
			return bias;
	}

	return 0;
}

static int compare_left(nat_char const *a,nat_char const *b)
{
	/* Compare two left-aligned numbers: the first to have a
	different value wins. */
	for (;; a++, b++)
	{
		if (!nat_isdigit(*a) && !nat_isdigit(*b))
			return 0;
		else if (!nat_isdigit(*a))
			return -1;
		else if (!nat_isdigit(*b))
			return +1;
		else if (*a < *b)
			return -1;
		else if (*a > *b)
			return +1;
	}

	return 0;
}

static int strnatcmp0(nat_char const *a, nat_char const *b, const bool fold_case)
{
	int ai, bi;
	nat_char ca, cb;
	int result;
	bool fractional;
	int sa, sb;
	
	assert(a && b);
	ai = bi = 0;
	fractional = false;

	while (1)
	{
		ca = a[ai]; cb = b[bi];

		/* skip over leading spaces or zeros */
		while (nat_isspace(ca))
			ca = a[++ai];

		while (nat_isspace(cb))
			cb = b[++bi];

		/* process run of digits */
		if (nat_isdigit(ca) && nat_isdigit(cb))
		{
			sa = sb = 0;

			if(!fractional)
			{
				while (ca == L'0')
				{
					ca = a[++ai]; sa++;
				}
				while (cb == L'0')
				{
					cb = b[++bi]; sb++;
				}
			}

			if (fractional)
			{
				if ((result = compare_left(a+ai, b+bi)) != 0)
					return result;
			}
			else
			{
				if ((result = compare_right(a+ai, b+bi)) != 0)
					return result;
			}

			/* on tie, the string with the longer leading zero's sequence wins */
			if(sa < sb)
				return -1;
			else if(sa > sb)
				return +1;
		}

		if (!ca && !cb)
		{
			/* The strings compare the same.  Perhaps the caller
			will want to call strcmp to break the tie. */
			return (fold_case) ? _wcsicmp(a, b) : wcscmp(a, b);
		}

		if (fold_case)
		{
			ca = nat_toupper(ca);
			cb = nat_toupper(cb);
		}

		if (ca < cb)
			return -1;
		else if (ca > cb)
			return +1;

		/* skipp leading zero's, unless previously seen char was a decimal point */
		fractional = nat_isdecpoint(ca) && nat_isdecpoint(cb);

		++ai; ++bi;
	}
}

int MUtils::Internal::NaturalSort::strnatcmp(nat_char const *a, nat_char const *b)
{
	return strnatcmp0(a, b, false);
}

/* Compare, recognizing numeric string and ignoring case. */
int MUtils::Internal::NaturalSort::strnatcasecmp(nat_char const *a, nat_char const *b)
{
	return strnatcmp0(a, b, true);
}
